Asbestos-cement pipe



Exarr June 22, 1943. a w. REMBERT ASBESTOS-CEMENT PIPE Filed May 29,1941 R Y mM M mm m vv w mw A HQ w Patented June 22, 1943 ExamASBESTOS-CEMENT PIPE Ernest Wayne Rembert, Plainfield, N. J., assignorto Johns-Manville Corporation, New York, N. Y., a corporation of NewYork Application May 29, 1941, Serial No. 395,712

2 Claims.

This invention relates to asbestos and cement pipe andthe method ofmaking the same, and is a continuation-in-part application of co-pendingapplication, Serial No. 131,585, filed March 18, 1937, now United StatesPatent No. 2,246,537, dated June 24, 1941.

Asbestos and cement pipes are in wide use for water lines or the like.Such pipes aremade in satisfactory manner by suspending asbestos fibresand Portland cement in a large volume of water, forming the suspendedmaterials into a web or thin sheet on a screen-faced cylinder mold,transferring the sheet to a cloth belt conveyor, transferring the sheetfrom the cloth to a mandrel, there winding the web upon itself, to forma tube, and subjecting the tube during the winding to strongcompression, to remove excess water and to compact and densify the pipethus formed. When the wall of thepipe has been made of the thicknessdesired, the pipe is removed from the mandrel and the cement ishardened.

In making such mandrel-compressed asbestos and cement pipe, there hasbeen used heretofore a proportion of asbestos of the order of to partsby weight to 100 parts of the combined dry weight of asbestos andPortland cement.

It is an object of the present invention to increase the averagestrength of asbestos and cement pipe of given wall thickness orconverselyto decrease the wall thickness and weight of pipe required fora given strength. Other objects and advantages will appear from thedetailed description that follows.

The invention comprises the hereinafter described novel features of theasbestos and cement pipe and the method of making it. More particularly,the invention comprises the method of making an asbestos and cement pipewhich includes forming upon a mandrel a wet asbestos and cement tube ofabnormally high proportion of asbestos fibres, at a pressuresubstantially in excess of that heretofore used.

A preferred embodiment of my product and method will be described inconnection with the attached drawing, to which reference is made.

Fig. 1 shows a diagrammatic side elevation of a suitable machine for usein practising the invention.

Fig. 2 shows a cross sectional view of the improved pipe.

In making the pipe ll, there is first formed an aqueous suspension of toparts by weight of the selected asbestos fibres of kind to be laterdescribed and 75 to 80 parts of Portland cement in a large volume ofwater, say, 2,500 to 5,000 parts. This suspension is then transferred,as by the pipe I2, to the leveling vat 13 provided with agitators I4. Inthis vat thereis maintained a small supply of the suspended asbestos andcement mixture which is passed, as used, into the cylinder mold vat IS.The cylinder mold vat contains the cylinder mold I6 and agitators IT.Water passes through the facing wire on the cylinder mold, thus causingthe deposition of a thin wet sheet or felt of solid material on thiswire. This felt is continuously transferred from the wire to an endlessbelt l8 at the zone of contact, under the couch roll is. The sheet onthe belt then passes continuously over a suction box 20, through which alarge portion of the water in the sheet is removed, and then to thepress section of the machine. Here the felt is transferred from the beltto the forming mandrel 2|. It is there spirally wrapped and compositedunder pressure with previously applied turns of the felt, to form thetube 26.

The belt, after losing the sheet to the mandrel, as described, thenreturns, over several tension and guide rolls, past washers 22 andbeater 30, and between the wringer rolls 23, to the cylinder mold. Therethe belt again picks up a thin felt of the wet asbestos and cementmixture. v

The press section of the machine includes a heavy bottom press roll 24on which the forming mandrel .rests during the formation of the pipe ortube 26. Acting upon the pipe on the mandrel are two smaller top pressrolls 21 and 28 which are rotatably mounted in a frame (not shown) thatis forced downwardly by the hydraulic pressure. These rolls arepermitted to rise as the thickness of the pipe increases, the pressureon the rolls being controlled by means of an automatic relief valve onthe hydraulic medium. An endless belt 29 travels around the two toppress rolls and loops over a sufflclent number of guide and tensionrolls to permit satisfactory manipulation and intermittent cleaning.

After the pipe 26 has been built up to the desired thicknes of wall, themachine is stopped, a thin-pointed tool is inserted between the insidesurface of the pipe and the surface of the forming mandrel, at each endthereof, the tool is withdrawn, the machine started, and the marldreland pipe supported thereon are rotated several times to loosen the pipeover the entire length of the mandrel. The pressure is then released onthe rolls 21 and 28, they are raised from position, the mandrel carryingthe pipe is taken out of position, asby being lifted from its supportsat either end or by being swung on the support at one end, as a pivot,and the pipe subsequently slipped from the mandrel.

The pipe is maintained in a suitable cradle and the Portland cementtherein is hardened.

Parts of the machine that are not illustrated are conventional.

Suitably, the suspension of asbestos fibres and Portland cement that hasbeen desc'r'i'b'edincludes also admixed silica. Thus, I have used toadvantage 30 toTUfparts of a relatively clean and sharp sand or finesilica to 100' parts of Portland cement.

When there is used the admixed silica, then the Portland cement in thepipe is cured by being subjected to steam at superatmospheric pressure,as, for example, at 70 to 120 pounds gage pressure per square inch.Under such conditions there is presumably conversion of the basicingredients of the Portland cement to monosilicates. The proportion ofthe admixed silica should be adequate theoretically, along with thesilica originally used in the manufacture of the Portland cement toconvert the basic ingredients thereof substantially completely tomonosilicates. Proportions of admixed silica in excess of 100 partsshould be avoided.

In the process described, a substantial part of th several substancesused in making the pipe, namely, asbestos Pprtlani-eemenwd sand, if thelatter is used, pass through the facing wire on the cylinder mold l6 andto a saveall tank (not shown). This material from the saveall tank isreturned to the vat l3 and there used to supply water and the saidsubstances, the proportion of such substances returned from the saveallto the total used being sometimes as high as one-half to three-quartersof the total.

With the reuse of such saveall material there is introduced into thepipe making machine asbestos fibres and Portland cement and sometimesalso sand that have previously been maintained in wet condition forvarious periods of time, say, on the average, for about 4 hours or so,this limited but substantial period of time being adequate to give onlyincipient hydration of the 'Portland cement.

This hydration, however, is suilicient to cause increased fiowability ofthe stock as wound upon the mandrel II, the effect of which increasedfiowability is corrected effectively by the negligible hydration of thePortland cement and asbestos fibres added to the process in dry form, atthe time they reach the winding step.

In making the asbestos and cement pipe, I use a relatively harsh,ii'e'ly'filtering fibre, such, for example, as erocidolite, Rhodesianchrysotile, Vimy Ridge (Canada) chrysotile, and/or Russian chrysotile.Such fibres may be used alone or in blends which may contain a limitedproportion of less harsh chrysotile from Asbestos, Canada, say,preferably in amount not exceeding substantially that of the selectedharsh fibre. The ratio of asbestos fibres to Portland cement may bevaried over a relatively wide range in manufac turing asbestos-cementpipes. However, inorder to obtain th beneficial results as describedherein it is preferable that the asbestos fibre to Portland cement ratiobe maintained within the range of 20-40 parts by weight of asbestosfibres to 100 parts dry weight of the combined asbestos fibres andPortland cement.

There have been used, in makingnsbestos and cement pipe by the presentmethod, relatively long fibres that, in the Quebec standard screen test,are rated 0-12-3-1, these figures referring, respectively, to the numberof ounces retained from a 16-ounee sample on approximately 2- mesh,4-mesh, and l0-mesh screens and the pan below the 10-mesh screen, in thestandard test. Somewhat shorter fibres may be used when the maximumstrength is not required.

In compressing the wet asbestos-cement tube, as it is being woundspirally upon itself on the forming mandrel ll, there is used a pressuresubstantially higher, as, for instance, about 50% to 100% higher thanthat heretofore used in making the same pipe sizes. Because of theimpossibility of stating exactly the pressure per square inch that isapplied to unit area of the stock being wound on itself, the followingdata from commercial operations are given to illustrat the meaning ofabnormally high pressure or pressure substantially greater than thatheretofore used."

When forming pipe approximately thirteen feet long, with a bottom pressroll of 25.5 inches diameter and two upper press rolls each of 7.5inches diameter, the said rolls and mandrel being approximately the samein length and the stock being wound completely along the mandrel exceptfor a few inches at either end thereof, the following maximum totalpressures have been used, with mandrels of the various diametersindicated.

Diameter of mandrel, inches (inside diameter of pipe machine to be made)pressure Tuna These maximum pressures ar used initially, during theearly stage of the winding operation, and are gradually decreased, say,by about 10 to 15 per cent during the winding operation.

For some purposes, the total pressures used may be less than those shownin the table by not of asbestos fibres of the kind described minimizesthe tendency of the stock to flow during the winding and compressionstep and become loose on the mandrel. In fact, it is this improvement inworking properties during manufacture that makes possible the use of theabnormally high pressures without premature loosening of the wound upmaterial from the mandrel.

The effect on density and strength of the pipe is illustrated by thefollowing test results for typical specimens of pipe made, respectively,by my improved and by the conventional method. The pipe specimens were 8inches in diameter and had walls 0.75 inch thick. They were made withoutthe addition of silica. In each case there was used asbestos fibres andPortland cement, all conditions of manufacture being the same except forvariation in the proportion of the fibres and total machine pressureapplied during the winding of the wet sheet material into the form of atube or a pipe. In each case, for instance, the pipe was cured underwater for- 10 days and then in air for 20 days before being tested andtests included a determination of the density of the wall of the pipeand the bursting strength under hydrostatic pressure. From the burstingstrength the tensile strength was calculated by the modified Bernieformula.

Efiect of proportion of fibre and pressure of fabrication on propertiesof pipe 23, 8? g gagg Properties of finished pipe Pipe No. 73;,

fibre and Bursting Tensile cement 1mm] Final strength strength Tom TamLbalsq. in. Lbalsq. in. 1 25 2A 22 900 5, 000 2 25 14 8 610 3, 250 3 l5l3 0 610 3, 250

The following tabulation illustrates the effect of high pressure andhigh fibre content upon the density of the product as compared toproducts manufactured under lower andequivalent fibre content anddifferent pressures:

Efiect of proportion of fibre and pressure of fabrication on the densityof the product gg g gg g x ggg Density, lbs. per cu. ft. Pipe weight ofs a N i to an orma cement Initial Final cum Dry Saturated Examistrengths are now used as the minimum basis for designingasbestos-cement pipes manufactured in accordance with the presentinvention. Heretofore,asbestos-cement pipes were designed on a muchlower'basis and in view thereof, the finished pipe product had muchlower strength.

Inasmuch as greatly increased strength is chformed under high pressureswill be substantially Lbs. per sq. inch 3 Inch 2,500 3 3,250 4 3,250 t3,6) 4,000 12 4,250 Above 12 The above minimum circumferential tensiletained in the product as a result of the present invention, applicanthas been able to reduce the wall thickness of asbestos-cement pipesabout 20% of the wall thickness of pipes containing approximately 15%fibre content and formed under the lower pressures referred to above.

On small sizes of pipe even greater improvement has been noted. Thus,the bursting strength in a typical run of 4-inch, thick-walled pipe wasdoubled by the change in pressure during manufacture and the abnormallyhigh proportion of fibres. Proportions of the fibres from 20 to 40 percent of the weight of the dry pipe may be used, the proportions above 25in this range being desirable if the pressure is increased substantiallyabove even the abnormally high pressure shown in the above table, as,for example, by to 100 per cent. I

In general, the pressure used with my proportion of asbestos fibresshould be not substantially less than two tons for each one inch ofdiameter of the mandrel. On the other hand, the maximum pressure usedshould be below that which ing 15% asbestos fibres, the wet strength ofthe pipe during formation is not adequate to permit an increase in theforming pressures over those used in previously known conventionalpractices. In order to facilitate the use of higher forming pressures,improved wet strength of the asbestoscement pipe can be obtained byincreasing the fibre content of the furnish, that is, approximately20-40% based on the dry weight of the mixed materials as describedabove. The increased fibre content at the same time provides greaterreinforcement in the structure which also contributes to increasedstrength. However, due to the greater bulking tendency of the highfibre' content it is necessary that higher forming pressures be utilizedin order to obtain comparable density to that obtainable onasbestos-cement pipes previously manufactured with low fibre content,that is, approximately 15% of the dry weight of the mixture.

The details given are for the purpose of illustration, not restriction,and variations within the spirit of the invention are intended to beincluded in the scope of the appended claims.

I claim:

1. Pipe comprising a highly compressed hydrated asbestos and Portlandcement composition in hardened condition, the proportion of asbestosbeing not less than 20 parts or more than 40 parts by weight to partsdry weight of the asbestos and cement. and said product being character-The only way by 40 parts by weight to 100 parts dry weight of said mixedmaterials and the proportion of ad mixed silica being not less thanabout 30 parts or more than 100 parts to 100 parts of the cement 5originally used.

ERNEST WAYNE REMBERT CERTIFICATE OF CORRECTION; atent Nd. 2,522,592,J1me 22,191

ERNEST WAYNE BEMBERL. I

It is herebg e i'tified that error appears in the printed gpecificatiionof the aboyanmnberefphteht requiring aorrection as follows: P151562,secand 1m; lin 58, in tho fiabl for themmeral ."5" ,read ---9-.-; -andthat the said Lqtters Pate nt should .be read with. unscprreqtionthereizi that the same may'-confdm,- to 'thereqord of the case in-thePate nt Office- Signed and sealed this 2l Lth day of August,: A; D 195-;

, Henry Van jArsdale, (S631) Acting commissioner'of Patents.

